'use strict';

// Ported from Stefan Gustavson's java implementation
// http://staffwww.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
// Sean McCullough banksean@gmail.com

var SimplexNoise = function(gen) {
    this.rand = gen;
    this.grad3 = [
	[1,1,0],[-1,1,0],[1,-1,0],[-1,-1,0],
	[1,0,1],[-1,0,1],[1,0,-1],[-1,0,-1],
	[0,1,1],[0,-1,1],[0,1,-1],[0,-1,-1]
    ];

    this.simplex = [
	[0,1,2,3],[0,1,3,2],[0,0,0,0],[0,2,3,1],[0,0,0,0],[0,0,0,0],
        [0,0,0,0],[1,2,3,0],[0,2,1,3],[0,0,0,0],[0,3,1,2],[0,3,2,1],
        [0,0,0,0],[0,0,0,0],[0,0,0,0],[1,3,2,0],[0,0,0,0],[0,0,0,0],
        [0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],
	[1,2,0,3],[0,0,0,0],[1,3,0,2],[0,0,0,0],[0,0,0,0],[0,0,0,0],
        [2,3,0,1],[2,3,1,0],[1,0,2,3],[1,0,3,2],[0,0,0,0],[0,0,0,0],
        [0,0,0,0],[2,0,3,1],[0,0,0,0],[2,1,3,0],[0,0,0,0],[0,0,0,0],
        [0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],
	[2,0,1,3],[0,0,0,0],[0,0,0,0],[0,0,0,0],[3,0,1,2],[3,0,2,1],
        [0,0,0,0],[3,1,2,0],[2,1,0,3],[0,0,0,0],[0,0,0,0],[0,0,0,0],
        [3,1,0,2],[0,0,0,0],[3,2,0,1],[3,2,1,0]
    ];
};

SimplexNoise.prototype.setSeed = function(seed) {
    this.p = [];
    this.rand.seed = seed;

    for (var i=0; i<256; i++) {
	this.p[i] = Math.floor(this.rand.nextRange(0, 255));
    }

    this.perm = [];
    for(var i=0; i<512; i++) {
	this.perm[i]=this.p[i & 255];
    }
};

SimplexNoise.prototype.dot = function(g, x, y) {
    return g[0]*x + g[1]*y;
};

SimplexNoise.prototype.noise = function(xin, yin) {
    var n0, n1, n2;

    var F2 = 0.5*(Math.sqrt(3.0)-1.0);
    var s = (xin+yin)*F2;
    var i = Math.floor(xin+s);
    var j = Math.floor(yin+s);
    var G2 = (3.0-Math.sqrt(3.0))/6.0;
    var t = (i+j)*G2;
    var X0 = i-t;
    var Y0 = j-t;
    var x0 = xin-X0;
    var y0 = yin-Y0;

    var i1, j1;
    if(x0>y0) {i1=1; j1=0;}
    else {i1=0; j1=1;}

    var x1 = x0 - i1 + G2;
    var y1 = y0 - j1 + G2;
    var x2 = x0 - 1.0 + 2.0 * G2;
    var y2 = y0 - 1.0 + 2.0 * G2;

    var ii = i & 255;
    var jj = j & 255;
    var gi0 = this.perm[ii+this.perm[jj]] % 12;
    var gi1 = this.perm[ii+i1+this.perm[jj+j1]] % 12;
    var gi2 = this.perm[ii+1+this.perm[jj+1]] % 12;

    var t0 = 0.5 - x0*x0-y0*y0;
    if(t0<0) n0 = 0.0;
    else {
	t0 *= t0;
	n0 = t0 * t0 * this.dot(this.grad3[gi0], x0, y0);
    }
    var t1 = 0.5 - x1*x1-y1*y1;
    if(t1<0) n1 = 0.0;
    else {
	t1 *= t1;
	n1 = t1 * t1 * this.dot(this.grad3[gi1], x1, y1);
    }
    var t2 = 0.5 - x2*x2-y2*y2;
    if(t2<0) n2 = 0.0;
    else {
	t2 *= t2;
	n2 = t2 * t2 * this.dot(this.grad3[gi2], x2, y2);
    }

    return 70.0 * (n0 + n1 + n2);
};

module.exports = SimplexNoise;
